Features Voltage Output: The battery development board supports 5V 3A or 3V 1A power supply output, as well as supports Micro USB 1.5A charging current. Circuit Protection: Mobile power supply with built in battery protection IC, with overcurrent, overvoltage, undervoltage, and over temperature protection. Applicable Range: This battery expansion board is mainly used for mobile power supply or other battery powered devices, which is efficient and practical. 4 Battery Capacity: This battery shield holder can install 4 pieces lithium batteries (not included) to ensure stable performance and high efficiency. Accurate Installation: Pay attention to the positive and negative poles of the battery during installation, and there are clear markings on the circuit board. Specification: Item Type: Battery Holder Material: PCB Battery: 4 x Lithium Battery (not included) Output Voltage: DC 5V 3A or DC 3V 1A Package List:1 x Battery Development Board Note:The normal operating voltage of the battery is 3.2V‑4.2V. Please do not connect the batteries in series, as this will increase the voltage. If you need to increase the battery capacity, you can connect them in parallel, but not in series! Package List 1 x Battery Development Board